Particle Size-Controlled Oxygen Reduction and Evolution Reaction Nanocatalysts Regulate Ru(bpy)32+'s Dual-potential Electrochemiluminescence for Sandwich

Multiple signal strategies remarkably improve the accuracy and efficiency of electrochemiluminescence (ECL) immunoassays, but the lack of potential-resolved luminophore pairs and chemical cross talk hinders their development. In this study, we synthesized a series of gold nanoparticles (AuNPs)/reduced graphene oxide (Au/rGO) composites as adjustable oxygen reduction reaction and oxygen evolution reaction catalysts to promote and modulate tris(2,2 ' -bipyridine) ruthenium(II) (Ru(bpy)32+)'s multisignal luminescence. With the increase in the diameter of AuNPs (3 to 30 nm), their ability to promote Ru(bpy)32+'s anodic ECL was first impaired and then strengthened, and cathodic ECL was first enhanced and then weakened. Au/ rGOs with medium-small and medium-large AuNP diameters remarkably increased Ru(bpy)32+'s cathodic and anodic luminescence, respectively. Notably, the stimulation effects of Au/rGOs were superior to those of most existing Ru(bpy)32+ co-reactants. Moreover, we proposed a novel ratiometric immunosensor construction strategy using Ru(bpy)32+'s luminescence promoter rather than luminophores as tags of antibodies to achieve signal resolution. This method avoids signal cross talk between luminophores and their respective co-reactants, which achieved a good linear range of 10-7to 10-1 ng/ml and a limit of detection of 0.33 fg/ml for detecting carcinoembryonic antigen. This study addresses the previous scarcity of the macromolecular co-reactants of Ru(bpy)32+, broadening its application in biomaterial detection. Furthermore, the systematic clarification of the detailed mechanisms for converting the potential-resolved luminescence of Ru(bpy)32+ could facilitate an in-depth understanding of the ECL process and should inspire new designs of Ru(bpy)32+ luminescence enhancers or applications of Au/ rGOs to other luminophores. This work removes some impediments to the development of multisignal ECL biodetection systems and provides vitality into their widespread applications.

Automated summary

In this study, gold nanoparticles/reduced graphene oxide (Au/rGO) composites were synthesized to promote and modulate the luminescence of tris(2,2 ' -bipyridine) ruthenium(II) (Ru(bpy)32+). The size of the gold nanoparticles affected the luminescence of Ru(bpy)32+. This method achieved a good linear range and a low limit of detection for detecting carcinoembryonic antigen.